Definition of "duad" []

• A unit of two objects; a pair. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "From the monad proceeds an indefinite duad, which is subordinate to the monad as to its cause."
• "Pythagorean system, to denote respectively the _monad_, or active principle of nature; the _duad_, or passive principle; the _triad_, or world emanating from their union; and the _quaterniad_, or intellectual science; the whole number of points amounting to ten, the symbol of perfection and consummation."
• "A figure used by Pythagoras, consisting of ten points, arranged in a triangular form so as to represent the monad, duad, triad, and quarterniad."